Zoom lens and image pickup apparatus using the same

ABSTRACT

A zoom lens includes in order from an object side to an image side, a first lens unit having a positive refractive power, a second lens unit having a negative refractive power, a third lens unit having a positive refractive power, and a fourth lens unit having a negative refractive power, and includes an aperture stop which is disposed between the second lens unit and the fourth lens unit, and the first lens unit includes a negative lens and a plurality of positive lenses, and at the time of zooming from a wide angle end to a telephoto end, a distance between the first lens unit and the second lens unit widens, a distance between the second lens unit and the third lens unit narrows, and a distance between the third lens unit and the fourth lens unit changes, and the zoom lens satisfies predetermined conditional expressions.

CROSS-REFERENCE TO RELATED APPLICATION

The present application is based upon and claims the benefit of priorityfrom the prior Japanese Patent Application No. 2013-015651 filed on Jan.30, 2013; the entire contents of which are incorporated herein byreference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a zoom lens and an image pickupapparatus using the same.

2. Description of the Related Art

As a zoom lens having a high zoom ratio, a zoom lens disclosed inJapanese Patent Application Laid-open Publication No. 2012-083472, andan image pickup apparatus using the same have hitherto been known.

SUMMARY OF THE INVENTION

A zoom lens according to a first aspect of the present inventioncomprises in order from an object side to an image side,

a first lens unit having a positive refractive power,

a second lens unit having a negative refractive power,

a third lens unit having a positive refractive power, and

a fourth lens unit having a negative refractive power, wherein

the zoom lens further includes

an aperture stop which is disposed between the second lens unit and thefourth lens unit, and

the first lens unit includes a negative lens and a plurality of positivelenses, and

at the time of zooming from a wide angle end to a telephoto end,

a distance between the first lens unit and the second lens unit widens,

a distance between the second lens unit and the third lens unit narrows,and a distance between the third lens unit and the fourth lens unitchanges, and

the following conditional expressions (1) and (2) are satisfied2.85<f _(t) /D _(G1ASt)<7.40  (1)0.2<D _(ASIMt) /f _(t)<0.40  (2)

where,

f_(t) denotes a focal length of the overall zoom lens system at thetelephoto end,

D_(G1ASt) denotes a distance on an optical axis from an object-sidesurface of a lens nearest to the object side in the first lens unit upto the aperture stop, at the telephoto end, and

D_(ASIMt) denotes a distance on the optical axis from the aperture stopup to an image, at the telephoto end.

A zoom lens according to a second aspect of the present inventioncomprises in order from an object side to an image side,

a first lens unit having a positive refractive power,

a second lens unit having a negative refractive power,

a third lens unit having a positive refractive power, and

a fourth lens unit having a negative refractive power, wherein

the zoom lens further includes

an aperture stop which is disposed between the second lens unit and thefourth lens unit, and

the first lens unit includes a negative lens and a plurality of positivelenses, and

at the time of zooming from a wide angle end to a telephoto end,

a distance between the first lens unit and the second lens unit widens,

a distance between the second lens unit and the third lens unit narrows,and

a distance between the third lens unit and the fourth lens unit changes,and

the following conditional expressions (1) and (3) are satisfied2.85<f _(t) /D _(G1ASt)<7.40  (1)0.16<D _(G2G3w) /D _(GlIMt)<0.6  (3)

where,

f_(t) denotes a focal length of the overall zoom lens system at thetelephoto end,

D_(G1ASt) denotes a distance on an optical axis from an object-sidesurface of a lens nearest to the object side in the first lens unit upto the aperture stop, at the telephoto end,

D_(G2G3w) denotes a distance on the optical axis between the second lensunit and the third lens unit at the wide angle end, and

D_(G1IMt) denotes a distance on the optical axis from the object-sidesurface of the lens nearest to the object side in the first lens unit upto an image, at the telephoto end.

A zoom lens according to a third aspect of the present inventioncomprises in order from an object side to an image side,

a first lens unit having a positive refractive power,

a second lens unit having a negative refractive power,

a third lens unit having a positive refractive power, and

a fourth lens unit having a negative refractive power, wherein

the zoom lens further includes

an aperture stop which is disposed between the second lens unit and thefourth lens unit, and

the first lens unit includes a negative lens and a plurality of positivelenses, and

at the time of zooming from a wide angle end to a telephoto end,

a distance between the first lens unit and the second lens unit widens,

a distance between the second lens unit and the third lens unit narrows,and

a distance between the third lens unit and the fourth lens unit changes,and

the following conditional expressions (1) and (4) are satisfied2.85<f _(t) /D _(G1ASt)<7.40  (1)0.05<(D _(G1IMt) −D _(G1Imw))/f _(t)<0.22  (4)

where,

f_(t) denotes a focal length of the overall zoom lens system at thetelephoto end,

D_(G1ASt) denotes a distance on an optical axis from an object-sidesurface of a lens nearest to the object side in the first lens unit upto the aperture stop, at the telephoto end,

D_(G1IMt) denotes a distance on the optical axis from an object-sidesurface of the lens nearest to the object side in the first lens unit upto an image, at the telephoto end,

D_(G1Imw) denotes a distance on the optical axis from the object-sidesurface of the lens nearest to the object side in the first lens unit upto the image, at the wide angle end.

A zoom lens according to a fourth aspect of the present inventioncomprises in order from an object side to an image side,

a first lens unit having a positive refractive power,

a second lens unit having a negative refractive power,

a third lens unit having a positive refractive power, and

a fourth lens unit having a negative refractive power, wherein

the zoom lens further includes

an image-side lens unit having a positive refractive power, which isdisposed on the image side of the fourth lens unit, and

an aperture stop which is disposed between the second lens unit and thefourth lens unit, and

the first lens unit includes a negative lens and a plurality of positivelenses, and

at the time of zooming from a wide angle end to a telephoto end,

a distance between the first lens unit and the second lens unit widens,

a distance between the second lens unit and the third lens unit narrows,and

a distance between the third lens unit and the fourth lens unit changes,and

a distance between the fourth lens unit and the image-side lens unitchanges, and

the first lens unit is positioned on the object side at the telephotoend, than a position at the wide angle end, and the image-side lens unitis positioned on the image side at the telephoto end, than a position atthe wide angle end, and the following conditional expression (1) issatisfied2.85<f _(t) /D _(G1ASt)<7.40  (1)

where,

f_(t) denotes a focal length of the overall zoom lens system at thetelephoto end, and

D_(G1ASt) denotes a distance on an optical axis from an object-sidesurface of a lens nearest to the object side in the first lens unit upto the aperture stop, at the telephoto end.

A zoom lens according to a fifth aspect of the present inventionincludes in order from an object side to an image side,

a first lens unit having a positive refractive power,

a second lens unit having a negative refractive power,

a third lens unit having a positive refractive power, and

a fourth lens unit having a negative refractive power, wherein

the zoom lens further includes

an aperture stop which is disposed between the second lens unit and thefourth lens unit, and

the first lens unit includes a negative lens and a plurality of positivelenses, and

at the time of zooming from a wide angle end to a telephoto end,

a distance between the first lens unit and the second lens unit widens,

a distance between the second lens unit and the third lens unit narrows,and

a distance between the third lens unit and the fourth lens unit changes,and

the following conditional expressions (1) and (5) are satisfied2.85<f _(t) /D _(G1ASt)<7.40  (1)20<f _(t) /f _(w)<50  (5)

where,

f_(t) denotes a focal length of the overall zoom lens system at thetelephoto end,

D_(G1ASt) denotes a distance on an optical axis from an object-sidesurface of a lens nearest to the object side in the first lens unit upto the aperture stop, at the telephoto end, and

f_(w) denotes a focal length of the overall zoom lens system at the wideangle end.

An image pickup apparatus according to the present invention comprises

a zoom lens, and

an image pickup element which is disposed on an image side of the zoomlens, and which converts an image formed by the zoom lens to an electricimage, wherein

the zoom lens is the zoom lens according to the first aspect of thepresent invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A, 1B, and 1C are cross sectional views of a zoom lens accordingto a first example of the present invention taken along its opticalaxis, showing its configuration in the state in which the zoom lens isfocused on an object point at infinity, where FIG. 1A shows the state atthe wide angle end, FIG. 1B shows the state in an intermediate focallength state, and FIG. 1C shows the state at the telephoto end;

FIGS. 2A, 2B, and 2C are cross sectional views of a zoom lens accordingto a second example of the present invention taken along its opticalaxis, showing its configuration in the state in which the zoom lens isfocused on an object point at infinity, where FIG. 2A shows the state atthe wide angle end, FIG. 2B shows the state in an intermediate focallength state, and FIG. 2C shows the state at the telephoto end;

FIGS. 3A, 3B, and 3C are cross sectional views of a zoom lens accordingto a third example of the present invention taken along its opticalaxis, showing its configuration in the state in which the zoom lens isfocused on an object point at infinity, where FIG. 3A shows the state atthe wide angle end, FIG. 3B shows the state in an intermediate focallength state, and FIG. 3C shows the state at the telephoto end;

FIGS. 4A, 4B, and 4C are cross sectional views of a zoom lens accordingto a fourth example of the present invention taken along its opticalaxis, showing its configuration in the state in which the zoom lens isfocused on an object point at infinity, where FIG. 4A shows the state atthe wide angle end, FIG. 4B shows the state in an intermediate focallength state, and FIG. 4C shows the state at the telephoto end;

FIGS. 5A, 5B, and 5C are cross sectional views of a zoom lens accordingto a fifth example of the present invention taken along its opticalaxis, showing its configuration in the state in which the zoom lens isfocused on an object point at infinity, where FIG. 5A shows the state atthe wide angle end, FIG. 5B shows the state in an intermediate focallength state, and FIG. 5C shows the state at the telephoto end;

FIGS. 6A to 6L are aberration diagrams of the zoom lens according to thefirst embodiment in the state in which the zoom lens is focused on anobject point at infinity;

FIGS. 7A to 7L are aberration diagrams of the zoom lens according to thesecond embodiment in the state in which the zoom lens is focused on anobject point at infinity;

FIGS. 8A to 8L are aberration diagrams of the zoom lens according to thethird embodiment in the state in which the zoom lens is focused on anobject point at infinity;

FIGS. 9A to 9L are aberration diagrams of the zoom lens according to thefourth embodiment in the state in which the zoom lens is focused on anobject point at infinity;

FIGS. 10A to 10L are aberration diagrams of the zoom lens according tothe fifth embodiment in the state in which the zoom lens is focused onan object point at infinity;

FIG. 11A and FIG. 11B are cross-sectional views of a digital camera inwhich, the zoom lens according to the present invention is installed,where, FIG. 11A is a cross-sectional view when collapsed to accommodate,and FIG. 11B is a cross-sectional view at the wide angle end;

FIG. 12 is a front perspective view showing an appearance of a digitalcamera as an image pickup apparatus;

FIG. 13 is a rear perspective view showing an appearance of the digitalcamera as an image pickup apparatus, and

FIG. 14 is a block diagram showing an internal circuit of maincomponents of the digital camera.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments of a zoom lens according to the present invention, and animage pickup apparatus in which the zoom lens is used will be describedbelow in detail by referring to the accompanying diagrams. However, thepresent invention is not restricted to the embodiments described below.

To start with, prior to explaining examples, an action and an effect ofthe zoom lens according to the present embodiment will be describedbelow.

The present embodiment is an embodiment having a basic arrangement ofthe aforementioned zoom lens, and further having arrangement of aspectsfrom the first aspect to the fifth aspect.

In the zoom lens according to the present embodiment, by making a zoomlens arrangement of four or more than four lens units, it is made to beadvantageous for securing zooming effect. Since a fourth lens unit islet to have a negative refractive power, the fourth lens unit magnifiesan image. In other words, it has a function of making the overall zoomlens small with respect to a size of an image plane. The overall lengthof the zoom lens is shortened while securing a high zoom ratio.

In the zoom lens according to the present embodiment, a first lens unitincludes three or more lenses, and both of a correction of chromaticaberration at a telephoto end and a correction of curvature of field ata wide angle end are carried out. A positive refractive power of thefirst lens unit is improved, and it also leads to shortening of anoverall length of the zoom lens at the telephoto end.

Moreover, by an aperture stop being disposed near a center of theoverall zoom lens, both of an aberration correction and small-sizing canbe carried out easily.

The zoom lens according to the present embodiment satisfies theaforementioned conditional expression (1).

Conditional expression (1) is an expression which specifies a preferablerelation of a focal length at the telephoto end and a position of theaperture stop at the telephoto end.

In the zoom lens according to the present embodiment, small-sizing in aradial direction of the first lens unit and reduction of a comaticaberration of a secondary spectrum at the telephoto end are carried outby making an arrangement such that a lower limit value does not fallbelow a lower limit of conditional expression (1). Moreover, alsoreduction of a chromatic aberration of magnification of a primaryspectrum at the telephoto end is carried out by making an arrangementsuch that an upper limit of conditional expression is not exceeded.

The zoom lens according to the present embodiment satisfies theaforementioned conditional expression (2).

Conditional expression (2) is an expression which specifies a preferablerelation of a distance from the aperture stop up to an image, and thefocal length at the telephoto end.

In the zoom lens according to the present embodiment, correction of thechromatic aberration of magnification of the primary spectrum at thetelephoto end is carried out by making an arrangement such that a lowerlimit value does not fall below a lower limit of conditional expression(2). Moreover, shortening of the overall length of the zoom lens andcorrection of a spherical aberration at the telephoto end are carriedout by making an arrangement such that an upper limit of conditionalexpression (2) is not exceeded.

The zoom lens according to the present embodiment satisfies theaforementioned conditional expression (3).

Conditional expression (3) is an expression which specifies a preferablerelation of a distance between a second lens unit and a third lens unitat the wide angle end, and the overall length of the zoom lens at thetelephoto end.

In the zoom lens according to the present embodiment, by making anarrangement such that a value does not fall below a lower limit ofconditional expression (3), the distance between the second lens unitand the third lens unit at the wide angle end is secured, and securingof zoom ratio and correction of curvature of field at the wide angle endare carried out. Moreover, by making an arrangement such that an upperlimit of conditional expression (3) is not exceeded, fluctuation in thecurvature of field from the wide angle end to the telephoto end issuppressed.

The zoom lens according to the present embodiment satisfies theaforementioned conditional expression (4).

Conditional expression (4) is an expression which specifies a preferablerelation of an amount of movement of the first lens unit with respect tothe image, and the focal length of the overall zoom lens system at thetelephoto end.

In the zoom lens according to the present embodiment, by making anarrangement such that a value does not fall below a lower limit ofconditional expression (4), the overall length of the zoom lens a thewide angle end is secured, and the curvature of field at the wide angleend is suppressed. Moreover, by making an arrangement such that an upperlimit of conditional expression (4) is not exceeded, the amount ofmovement of the first lens unit is suppressed, and the fluctuation inthe curvature of field from the wide angle end to the telephoto end issuppressed.

In the zoom lens according to the present embodiment, an arrangement ismade such that an image-side lens unit (a fifth lens unit) having apositive refractive power is disposed on an image side of a fourth lensunit having a negative refractive power, and an exit pupil is kept at adistance from an image plane.

A distance between the fourth lens unit and the image-side lens unitchanges, the first lens unit is positioned on an object side at the wideangle end than a position at the wide angle end, and the image-side lensunit is positioned on the image side at the telephoto end than aposition at the wide angle end.

By moving the first lens unit, a function of increasing magnification ofthe second lens unit is secured. Moreover, by carrying out an operationof increasing magnification by moving the image-side lens unit, a loadof zooming on other lens units is reduced. An amount of movement of thelens units which move at the time of zooming is suppressed, and afluctuation in the curvature of field and the spherical aberration withzooming is suppressed.

The zoom lens according to the present embodiment satisfies theaforementioned conditional expression (5).

Conditional expression (5) is an expression which specifies a preferablezoom ratio.

In the zoom lens according to the present embodiment, by making anarrangement such that a value does not fall below a lower limit ofconditional expression (5), the zoom lens is let to be a zoom lens inwhich, a change in an angle of view is secured sufficiently.Particularly, super telephoto-region photography is made possible.Moreover, by making an arrangement such that an upper limit ofconditional expression (5) is not exceeded, reduction of the overalllength at the telephoto end and securing brightness at the telephoto endcan be carried out easily.

In the zoom lens according to the present embodiment, the second lensunit satisfies the following conditional expression (6).−0.06<f _(G2) /f _(t)<−0.03  (6)

where,

f_(G2) denotes a focal length of the second lens unit.

Conditional expression (6) is an expression which specifies thepreferable focal length of the second lens unit with respect to thefocal length at the telephoto end.

In the zoom lens according to the present embodiment, by making anarrangement such that a value does not fall below a lower limit ofconditional expression (6), the fluctuation in the curvature of fieldfrom the wide angle end to the telephoto end is suppressed. Moreover, bymaking an arrangement such that an upper limit of conditional expression(6) is not exceeded, the curvature of field at the wide angle end issuppressed.

The zoom lens according to the present embodiment satisfies thefollowing conditional expressions (5-1) and (7).23<f _(t) /f _(w)<50  (5-1)0.010<D _(G1G223) /f _(w)<0.07  (7)

where,

D_(G1G223) denotes a distance between the first lens unit and the secondlens unit, in an arbitrary state in which, the focal length becomesshorter than f_(t)/23.

In an arrangement in which the zoom ratio exceeds 23 in order to satisfyconditional expression (5-1), the distance between the first lens unitand the second lens unit satisfies conditional expression (7).

By making an arrangement such that a value does not fall below a lowerlimit of conditional expression (7), the fluctuation in the curvature offield from the wide angle end to the telephoto end is suppressed. Bymaking an arrangement such that an upper limit of conditional expression(7) is not exceeded, the curvature of field at the wide angle end issuppressed.

An embodiment such as Example 1 and Example 4, in which the zoom ratioexceeds 28, satisfies the following conditional expressions (5-2) and(8).28<f _(t) /f _(w)<50  (5-2)0.010<D _(G1G228) /f _(w)<0.07  (8)

where,

D_(G1G228) denotes a distance between the first lens unit and the secondlens unit, in an arbitrary state in which, the focal length is shorterthan f_(t)/28.

In an arrangement in which, the zoom ratio exceeds 28 in order tosatisfy conditional expression (5-2), the distance between the firstlens unit and the second lens unit satisfies conditional expression (8).

By making an arrangement such that a value does not fall below a lowerlimit of conditional expression (8), the fluctuation in the curvature offield from the wide angle end to the telephoto end is suppressed. Bymaking an arrangement such that an upper limit of conditional expression(8) is not exceeded, the curvature of field at the wide angle end issuppressed.

In the zoom lens according to the present embodiment, the first lensunit is positioned on the object side at the telephoto end, than aposition at the wide angle end, the second lens unit is positioned onthe image side at the telephoto end, than a position at the wide angleend, the third lens unit is positioned on the object side at thetelephoto end, than a position at the wide angle end, and the fourthlens unit is positioned on the object side at the telephoto end, than aposition at the wide angle end.

Accordingly, it is possible to make small an amount of movement of eachlens unit, and it is easy to make short a drive mechanism (such as alens barrel) which moves the lens units, thereby achieving both, a highzoom ratio and thinning when collapsed to accommodate.

In the zoom lens according to the present embodiment, the aperture stopis disposed immediately before the object side of the third lens unit,and the third lens unit and the aperture stop move integrally along anoptical axis and are positioned on the object side at the telephoto endthan a position at the wide angle end.

Accordingly, small-sizing in a radial direction of the third lens unit,small-sizing of the first lens unit and the second lens unit, and anadjustment of the exit pupil of the zoom lens are carried out.

In the zoom lens according to the present invention, the second lensincludes maximum of three lenses. Accordingly, it is an arrangementwhich is advantageous for a low cost, and small-sizing when collapsed toaccommodate.

Moreover, the third lens unit includes maximum of four lenses.Consequently, it is an arrangement which is advantageous for a low cost,and small-sizing when collapsed to accommodate.

Moreover, the fourth lens unit includes one lens component.

Here, the lens component is a lens block of which, only two surfacesnamely, an object-side surface and an image-side surface make a contactwith air, in an optical path.

Accordingly, it is an arrangement which is advantageous for low cost,and small-sizing when collapsed to accommodate.

The zoom lens according to the present embodiment is a five-unit zoomlens in which, an image-side lens unit having a positive refractivepower is disposed on the image side of the fourth lens unit, and at thetime of zooming from the wide angle end to the telephoto end, a distancebetween the fourth lens unit and the image-side lens unit changes.

By disposing the image-side lens unit, the exit pupil is kept at adistance from the image. Accordingly, an angle of incidence of a lightray on an electronic image pickup element is suppressed, and anoccurrence of chromatic shading is suppressed.

In the zoom lens according to the present embodiment, the image-sidelens unit includes one lens component. Consequently, it is anarrangement which is advantageous for low cost, and small sizing whencollapsed to accommodate.

An image pickup apparatus according to the present embodiment includes

a zoom lens, and

an image pickup element which is disposed on an image side of the zoomlens, and which converts an image formed by the zoom lens to an electricsignal, and

the zoom lens is one of the aforementioned zoom lenses.

Accordingly, it is an image pickup apparatus in which a zoom ratio andan optical performance are secured, and small-sizing is possible.

The image pickup apparatus according to the present embodiment furtherhas on an object side of the first lens unit, a lens barrier sectionhaving a plurality of barrier members which retract in a directionperpendicular to an optical axis.

Since an effective diameter of the first lens unit is made small, bydisposing the lens barrier portion which retracts (may be by a linearmovement or by a rotational movement) in the direction perpendicular tothe optical axis, a portability and an operability are improved.

It is preferable that a plurality of the above-mentioned arrangements issatisfied simultaneously.

For each conditional expression, by specifying one of or both of anupper limit value and a lower limit value as shown below, it is possibleto make an effect more assured.

For conditional expression (1), it is more preferable to let a lowerlimit value to be 2.9, and 3.0 is even more preferable. Moreover, forconditional expression (1) it is more preferable to let an upper limitvalue to be 5.5, and 4.0 is even more preferable.

For conditional expression (2), it is more preferable to let a lowerlimit value to be 0.23, and 0.26 is even more preferable. Moreover, forconditional expression (2), it is more preferable to let an upper limitvalue to be 0.38, and 0.37 is even more preferable.

For conditional expression (3), it is more preferable to let a lowerlimit value to be 0.20, and 0.22 is even more preferable, and 0.23 isall the more preferable. Moreover, for conditional expression (3), it ismore preferable to let an upper limit value to be 0.45, and 0.31 is evenmore preferable.

For conditional expression (4), it is more preferable to let a lowerlimit value to be 0.08, and 0.10 is even more preferable. Moreover, forconditional expression (4), it is more preferable to let an upper limitvalue to be 0.21, and 0.20 is even more preferable.

For conditional expression (5), it is more preferable to let a lowerlimit value to be 23, and 28 is even more preferable. Moreover, forconditional expression (5), it is more preferable to let an upper limitvalue to be 40, and 35 is even more preferable.

For conditional expression (6), it is more preferable to let a lowerlimit value to be −0.057. Moreover, for conditional expression (6), itis more preferable to let an upper limit value to be −0.04.

For conditional expression (7), it is more preferable to let a lowerlimit value to be 0.03, and 0.05 is even more preferable. Moreover, forconditional expression (7), it is more preferable to let an upper limitvalue to be 0.071.

For conditional expression (8), it is more preferable to let a lowerlimit value to be 0.03, and 0.05 is even more preferable, and 0.06 isall the more preferable. Moreover, for conditional expression (8), it ismore preferable to let an upper limit value to be 0.071.

EXAMPLES

Examples from an example 1 to example 5 of the zoom lens according tothe present invention will be described below. FIG. 1A, FIG. 1B, andFIG. 1C are lens cross-sectional views along an optical axis showing anoptical arrangement at the time of infinite object point focusing of azoom lens according to the example 1 of the present invention, where,FIG. 1A shows a state at a wide angle end, FIG. 1B shows an intermediatestate, and FIG. 1C shows a state at a telephoto end. FIG. 2A, FIG. 2B,and FIG. 2C are lens cross-sectional views along an optical axis showingan optical arrangement at the time of infinite object point focusing ofa zoom lens according to the example 2 of the present invention, where,FIG. 2A shows a state at a wide angle end, FIG. 2B shows an intermediatestate, and FIG. 2C shows a state at a telephoto end. FIG. 3A, FIG. 3B,and FIG. 3C are lens cross-sectional views along an optical axis showingan optical arrangement at the time of infinite object point focusing ofa zoom lens according to the example 3 of the present invention, where,FIG. 3A shows a state at a wide angle end, FIG. 3B shows an intermediatestate, and FIG. 3C shows a state at a telephoto end. FIG. 4A, FIG. 4B,and FIG. 4C are lens cross-sectional views along an optical axis showingan optical arrangement at the time of infinite object point focusing ofa zoom lens according to the example 4 of the present invention, where,FIG. 4A shows a state at a wide angle end, FIG. 4B shows an intermediatestate, and FIG. 4C shows a state at a telephoto end. FIG. 5A, FIG. 5B,and FIG. 5C are lens cross-sectional views along an optical axis showingan optical arrangement at the time of infinite object point focusing ofa zoom lens according to the example 5 of the present invention, where,FIG. 5A shows a state at a wide angle end, FIG. 5B shows an intermediatestate, and FIG. 5C shows a state at a telephoto end. In diagrams fromFIG. 1A to FIG. 5C, a first lens unit is denoted by G1, a second lensunit is denoted by G2, a third lens unit is denoted by G3, a fourth lensunit is denoted by G4, a fifth lens unit is denoted by G5, an aperturestop is denoted by S, a flat parallel plate which forms a low-passfilter on which, a wavelength region restricting coating which restrictsinfrared rays is applied is denoted by F, a flat parallel plate of coverglass is denoted by C, and an image plane is denoted by I. A multi-layerfilm for restricting wavelength region may be applied to a surface ofthe cover glass C. Moreover, an arrangement may be made to impart aneffect of a low-pass filter to the cover glass C.

Moreover, in each example, the aperture stop S moves integrally with thethird lens unit G3, toward the object side. All numerical data is datain a state when focused at an object at an infinite distance. A unit oflength of each numerical value is mm and a unit of angle is ° (degrees).Focusing in each example is to be carried out by moving a fourth lensunit G4. Furthermore, zoom data are values at a wide angle end (wideangle), in an intermediate focal length state (intermediate), and at atelephoto end (telephoto).

A zoom lens according to the example 1, as shown in FIG. 1A, FIG. 1B,and FIG. 1C, includes in order from an object side, a first lens unit G1having a positive refractive power, a second lens unit G2 having anegative refractive power, an aperture stop S, a third lens unit G3having a positive refractive power, a fourth lens unit G4 having anegative refractive power, and a fifth lens unit G5 having a positiverefractive power.

At the time of zooming from a wide angle end to a telephoto end, thefirst lens unit G1 moves toward the object side. The second lens unit G2moves toward an image side. The third lens unit G3 moves toward theobject side. The fourth lens unit G4 moves toward the object side. Thefifth lens unit G5 moves toward the image side.

In order from the object side, the first lens unit G1 includes anegative meniscus lens L1 having a convex surface directed toward theobject side, a biconvex positive lens L2, and a positive meniscus lensL3 having a convex surface directed toward the object side. Here, thenegative meniscus lens L1 and the biconvex positive lens L2 are cementedmutually. The second lens unit G2 includes a negative meniscus lens L4having a convex surface directed toward the object side, a biconcavenegative lens L5, and a biconvex positive lens L6. The third lens unitG3 includes a biconvex positive lens L7, a negative meniscus lens L8having a convex surface directed toward the object side, and a biconvexpositive lens L9. Here, the negative meniscus lens L8 and the biconvexpositive lens L9 are cemented mutually. The fourth lens unit G4 includesa biconcave negative lens L10. The fifth lens unit G5 includes abiconvex positive lens L11.

An aspheric surface is provided to six surfaces namely, both surfaces ofthe biconcave negative lens L5, both surfaces of the biconvex positivelens L7, and both surfaces of the biconvex positive lens L11.

A zoom lens according to the example 2, as shown in FIG. 2A, FIG. 2B,and FIG. 2C, includes in order from an object side, a first lens unit G1having a positive refractive power, a second lens unit G2 having anegative refractive power, an aperture stop S, a third lens unit G3having a positive refractive power, a fourth lens unit G4 having anegative refractive power, and a fifth lens unit G5 having a positiverefractive power.

At the time of zooming from a wide angle end to a telephoto end, thefirst lens unit G1 moves toward the object side. The second lens unit G2moves toward an image side. The third lens unit G3 moves toward theobject side. The fourth lens unit G4 moves toward the object side. Thefifth lens unit G5 moves toward the image side.

In order from the object side, the first lens unit G1 includes anegative meniscus lens L1 having a convex surface directed toward theobject side, a biconvex positive lens L2, and a positive meniscus lensL3 having a convex surface directed toward the object side. The secondlens unit G2 includes a negative meniscus lens L4 having a convexsurface directed toward the object side, a biconcave negative lens L5,and a biconvex positive lens L6. The third lens unit G3 includes abiconvex positive lens L7, a biconvex positive lens L8, a biconcavenegative lens L9, and a biconvex positive lens L10. Here, the biconvexpositive lens L8 and the biconcave negative lens L9 are cementedmutually. The fourth lens unit G4 includes a biconcave negative lensL11. The fifth lens unit G5 includes a biconvex positive lens L12.

An aspheric surface is provided to five surfaces namely, a surface onthe object side of the biconcave negative lens L5, a surface on theimage side of the biconvex positive lens L6, both surfaces of thebiconvex positive lens L7, and a surface on the image side of thebiconvex positive lens L12.

A zoom lens according to the example 3, as shown in FIG. 3A, FIG. 3B,and FIG. 3C, includes in order from an object side, a first lens unit G1having a positive refractive power, a second lens unit G2 having anegative refractive power, an aperture stop S, a third lens unit G3having a positive refractive power, a fourth lens unit G4 having anegative refractive power, and a fifth lens unit G5 having a positiverefractive power.

At the time of zooming from a wide angle end to a telephoto end, thefirst lens unit G1 moves toward the object side. The second lens unit G2moves toward an image side. The third lens unit G3 moves toward theobject side. The fourth lens unit G4 moves toward the object side. Thefifth lens unit G5 moves toward the image side.

In order from the object side, the first lens unit G1 includes anegative meniscus lens L1 having a convex surface directed toward theobject side, a planoconvex positive lens L2 having a convex surfacedirected toward the object side, and a positive meniscus lens L3 havinga convex surface directed toward the object side. Here, the negativemeniscus lens L1 and the planoconvex positive lens L2 are cementedmutually. The second lens unit G2 includes a negative meniscus lens L4having a convex surface directed toward the object side, a biconcavenegative lens L5, and a biconvex positive lens L6. The third lens unitG3 includes a biconvex positive lens L7, a negative meniscus lens L8having a convex surface directed toward the object side, and a biconvexpositive lens L9. Here, the negative meniscus lens L8 and the biconvexpositive lens L9 are cemented mutually. The fourth lens unit G4 includesa biconcave negative lens L10. The fifth lens unit G5 includes abiconvex positive lens L11.

An aspheric surface is provided to six surfaces namely, both surfaces ofthe biconcave negative lens L5, both surfaces of the biconvex positivelens L7, and both surfaces of the biconvex positive lens L11.

A zoom lens according to the example 4, as shown in FIG. 4A, FIG. 4B,and FIG. 4C, includes in order from an object side, a first lens unit G1having a positive refractive power, a second lens unit G2 having anegative refractive power, an aperture stop S, a third lens unit G3having a positive refractive power, a fourth lens unit G4 having anegative refractive power, and a fifth lens unit G5 having a positiverefractive power.

At the time of zooming from a wide angle end to a telephoto end, thefirst lens unit G1 moves toward the object side. The second lens unit G2moves toward an image side. The third lens unit G3 moves toward theobject side. The fourth lens unit G4 moves toward the object side. Thefifth lens unit G5 moves toward the image side.

In order from the object side, the first lens unit G1 includes anegative meniscus lens L1 having a convex surface directed toward theobject side, a biconvex positive lens L2, and a positive meniscus lensL3 having a convex surface directed toward the object side. Here, thenegative meniscus lens L1 and the biconvex positive lens L2 are cementedmutually. The second lens unit G2 includes a negative meniscus lens L4having a convex surface directed toward the object side, a biconcavenegative lens L5, and a biconvex positive lens L6. The third lens unitG3 includes a biconvex positive lens L7, a negative meniscus lens L8having a convex surface directed toward the object side, and a biconvexpositive lens L9. Here, the negative meniscus lens L8 and the biconvexpositive lens L9 are cemented mutually. The fourth lens unit G4 includesa biconcave negative lens L10. The fifth lens unit G5 includes abiconvex positive lens L11.

An aspheric surface is provided to six surfaces namely, both surfaces ofthe biconcave negative lens L5, both surfaces of the biconvex positivelens L7, and both surfaces of the biconvex positive lens L11.

A zoom lens according to the example 5, as shown in FIG. 5A, FIG. 5B,and FIG. 5C, includes in order from an object side, a first lens unit G1having a positive refractive power, a second lens unit G2 having anegative refractive power, an aperture stop S, a third lens unit G3having a positive refractive power, a fourth lens unit G4 having anegative refractive power, and a fifth lens unit G5 having a positiverefractive power.

At the time of zooming from a wide angle end to a telephoto end, thefirst lens unit G1 moves toward the object side. The second lens unit G2moves toward an image side. The third lens unit G3 moves toward theobject side. The fourth lens unit G4, after moving toward the imageside, moves toward the object side. The fifth lens unit G5 moves towardthe image side.

In order from the object side, the first lens unit G1 includes anegative meniscus lens L1 having a convex surface directed toward theobject side, a positive meniscus lens L2 having a convex surfacedirected toward the object side, and a positive meniscus lens L3 havinga convex surface directed toward the object side. The second lens unitG2 includes a negative meniscus lens L4 having a convex surface directedtoward the object side, a biconcave negative lens L5, and a biconvexpositive lens L6. The third lens unit G3 includes a biconvex positivelens L7, a negative meniscus lens L8 having a convex surface directedtoward the object side, and a biconvex positive lens L9. Here, thenegative meniscus lens L8 and the biconvex positive lens L9 are cementedmutually. The fourth lens unit G4 includes a biconcave negative lensL10. The fifth lens unit G5 includes a biconvex positive lens L11.

An aspheric surface is provided to six surfaces namely, both surfaces ofthe biconcave negative lens L5, both surfaces of the biconvex positivelens L7, and both surfaces of the biconvex positive lens L11.

Numerical data of each embodiment described above is shown below. Apartfrom symbols described above, fb denotes a back focus, f1, f2, . . .denotes a focal length of each lens unit, FNO denotes an F number, codenotes a half image angle, WE denotes a wide angle end, ST denotes anintermediate state, TE denotes a telephoto end, r denotes radius ofcurvature of each lens surface, d denotes a distance between two lenses,nd denotes a refractive index of each lens for a d-line, and vd denotesan Abbe's number for each lens. The overall length of the lens systemwhich will be described later is a length which is obtained by addingthe back focus to a distance from the first lens surface up to the lastlens surface. fb (back focus) is a unit which is expressed upon airconversion of a distance from the last lens surface up to a paraxialimage plane.

A shape of the aspheric surface is described by the following expression(I) using each aspherical surface coefficient in each embodiment, when Zis let to be an optical axis in which a light passing direction is letto be a positive direction, and Y is let to be a direction orthogonal tothe optical axis.Z=(Y ² /r)/[1+{1−(K+1)(Y/r)²}^(1/2) ]+A ₄ Y ⁴+A ₆ Y ⁶ +A ₈ Y ⁸ +A ₁₀ Y¹⁰  (I)

where, r denotes a paraxial radius of curvature, K denotes a conicalcoefficient, A₄, A₆, A₈, and A₁₀ denote aspherical surface coefficientsof a fourth order, a sixth order, an eight order, a tenth order, and atwelfth order respectively. Moreover, in the aspherical surfacecoefficients, ‘e-n’ (where, n is an integral number) indicates‘10^(−n’.)

Example 1

unit mm Surface data Surface No r d nd νd Object plane ∞ ∞  1 38.5510.80 1.91082 35.25  2 22.771 3.30 1.49700 81.54  3 −313.298 0.10  420.122 2.42 1.49700 81.54  5 70.096 Variable  6 200.000 0.30 1.9108235.25  7 6.188 2.85  8* −10.241 0.40 1.74320 49.34  9* 18.541 0.10 1013.845 1.55 1.94595 17.98 11 −54.863 Variable 12(stop) ∞ 0.66 13* 7.9312.14 1.58313 59.38 14* −20.215 1.83 15 439.840 0.40 1.91082 35.25 166.873 2.15 1.49700 81.54 17 −8.668 Variable 18 −16.437 0.50 1.5311055.91 19 15.006 Variable 20* 241.479 2.15 1.53110 55.91 21* −8.401Variable 22 ∞ 0.30 1.51633 64.14 23 ∞ 0.40 24 ∞ 0.50 1.51633 64.14 25 ∞0.53 Image plane ∞ (Image pickup surface) Aspherical surface data 8thsurface K = 0.000 A4 = 3.07582e−04, A6 = 7.40085e−07, A8 = −2.43096e−079th surface K = 0.000 A4 = 3.13493e−04, A6 = −6.29781e−06 13th surface K= 0.000 A4 = −1.86188e−04, A6 = 1.33104e−06, A8 = −6.54846e−08, A10 =1.60686e−09 14th surface K = 0.000 A4 = 4.20720e−04, A6 = −4.71232e−0720th surface K = 0.000 A4 = −4.57271e−04 21th surface K = 0.000 A4 =2.57842e−05, A6 = 2.01462e−06, A8 = −3.08194e−08 Zoom data WE ST TEFocal length 4.55 23.21 131.12 Fno. 2.87 4.96 6.70 Angle of field 2ω90.10 18.16 3.38 fb (in air) 7.62 5.80 2.44 Lens total length (in air)54.77 70.02 78.15 d5 0.30 15.18 27.32 d11 18.77 7.44 0.54 d17 3.28 8.148.78 d19 3.16 11.81 17.42 d21 6.17 4.34 0.98 Unit focal length f1 =40.41 f2 = −5.79 f3 = 10.62 f4 = −14.69 f5 = 15.33

Example 2

unit mm Surface data Surface No r d nd νd Object plane ∞ ∞  1 33.5670.80 1.90366 31.32  2 22.034 0.10  3 21.741 3.27 1.49700 81.54  4−192.340 0.10  5 20.250 2.12 1.49700 81.54  6 59.103 Variable  7 58.2510.40 2.00100 29.13  8 7.218 2.61  9* −8.657 0.50 1.72903 54.04 10 14.1740.10 11 12.028 1.54 2.10300 18.05 12* −439.898 Variable 13(stop) ∞ 1.0014* 5.858 2.23 1.59201 67.02 15* −23.759 0.21 16 12.131 1.65 1.5713552.95 17 −22.447 0.30 1.91082 35.25 18 4.526 0.14 19 4.919 1.96 1.5311055.91 20 −9.008 Variable 21 −39.250 0.40 1.72916 54.68 22 6.719 Variable23 106.839 2.00 1.72903 54.04 24* −11.187 Variable 25 ∞ 0.30 1.5163364.14 26 ∞ 0.40 27 ∞ 0.50 1.51633 64.14 28 ∞ 0.53 Image plane ∞ (Imagepickup surface) Aspherical surface data 9th surface K = 0.000 A4 =1.57145e−04, A6 = 4.11375e−06 12th surface K = 0.000 A4 = 1.76543e−04,A6 = 2.42062e−06 14th surface K = 0.000 A4 = −3.04061e−04, A6 =2.75626e−06 15th surface K = 0.000 A4 = 6.78578e−04, A6 = 2.81900e−0624th surface K = 0.000 A4 = 2.19744e−04, A6 = −2.04406e−06 Zoom data WEST TE Focal length 4.55 21.86 104.86 Fno. 3.03 5.09 6.64 Angle of field2ω 87.86 19.20 4.16 fb (in air) 6.25 4.53 2.45 Lens total length (inair) 50.16 56.33 65.72 d6 0.25 11.03 22.62 d12 18.54 5.70 0.10 d20 1.925.00 4.45 d22 1.77 8.63 14.67 d24 4.83 3.05 1.00 Unit focal length f1 =36.27 f2 = −5.90 f3 = 8.18 f4 = −7.84 f5 = 13.99

Example 3

unit mm Surface data Surface No r d nd νd Object plane ∞ ∞  1 31.4560.70 1.91082 35.25  2 18.784 2.56 1.49700 81.54  3 ∞ 0.15  4 17.827 2.111.49700 81.54  5 83.811 Variable  6 200.000 0.30 1.83481 42.71  7 5.0692.80  8* −9.371 0.40 1.74156 49.21  9* 23.371 0.10 10 15.463 1.251.94595 17.98 11 −50.853 Variable 12(stop) ∞ 0.66 13* 6.841 1.87 1.5831359.38 14* −14.028 1.55 15 108.155 0.40 1.91082 35.25 16 5.565 2.011.49700 81.54 17 −8.603 Variable 18 −23.868 0.50 1.53110 55.91 19 10.707Variable 20* 5407.914 1.90 1.53110 55.91 21* −8.677 Variable 22 ∞ 0.301.51633 64.14 23 ∞ 0.40 24 ∞ 0.50 1.51633 64.14 25 ∞ 0.53 Image plane ∞(Image pickup surface) Aspherical surface data 8th surface K = 0.000 A4= 4.01038e−04, A6 = −8.36025e−06, A8 = −4.92569e−07 9th surface K =0.000 A4 = 2.35077e−04, A6 = −1.57539e−05 13th surface K = 0.000 A4 =−4.86266e−04, A6 = 5.75719e−06, A8 = −1.27642e−06 14th surface K = 0.000A4 = 4.56002e−04, A6 = 1.29630e−06, A8 = −1.18507e−06 20th surface K =0.000 A4 = −2.91616e−04 21th surface K = 0.000 A4 = 1.80978e−04, A6 =−3.29481e−09, A8 = −1.02926e−08 Zoom data WE ST TE Focal length 4.4120.82 101.70 Fno. 3.20 5.35 6.90 Angle of field 2ω 91.70 20.12 4.32 fb(in air) 7.33 5.52 2.57 Lens total length (in air) 48.41 59.46 67.90 d50.31 11.93 22.70 d11 15.60 5.53 0.54 d17 1.47 6.12 6.33 d19 4.45 11.1016.51 d21 5.87 4.06 1.10 Unit focal length f1 = 34.64 f2 = −5.07 f3 =8.99 f4 = −13.85 f5 = 16.31

Example 4

unit mm Surface data Surface No r d nd νd Object plane ∞ ∞  1 33.9930.70 1.91082 35.25  2 20.432 2.55 1.49700 81.54  3 −1195.431 0.15  419.471 2.10 1.49700 81.54  5 96.944 Variable  6 51750.697 0.32 1.9108235.25  7 6.034 2.70  8* −10.572 0.40 1.74156 49.21  9* 18.207 0.10 1014.599 1.45 1.94595 17.98 11 −42.442 Variable 12(stop) ∞ 0.66 13* 6.1231.87 1.58313 59.38 14* −17.594 1.25 15 281.206 0.40 1.91082 35.25 164.500 2.10 1.58313 59.38 17 −12.416 Variable 18 −30.599 0.40 1.5311055.91 19 8.315 Variable 20* 5060.788 2.05 1.53110 55.91 21* −8.850Variable 22 ∞ 0.30 1.51633 64.14 23 ∞ 0.40 24 ∞ 0.50 1.51633 64.14 25 ∞0.53 Image plane ∞ (Image pickup surface) Aspherical surface data 8thsurface K = 0.000 A4 = 6.95097e−05, A6 = 2.13361e−06 9th surface K =0.000 A4 = 1.32456e−06, A6 = 2.15510e−06 13th surface K = 0.000 A4 =−3.46827e−04, A6 = −2.72804e−06, A8 = −5.85149e−09 14th surface K =0.000 A4 = 4.71774e−04, A6 = −4.72805e−06, A8 = 1.84083e−07 20th surfaceK = 0.000 A4 = −2.64793e−04 21th surface K = 0.000 A4 = 1.05141e−04, A6= 1.89001e−07, A8 = −6.95062e−09 Zoom data WE ST TE Focal length 4.6223.76 132.20 Fno. 3.36 5.49 7.44 Angle of field 2ω 89.90 19.80 3.36 fb(in air) 7.16 5.70 1.85 Lens total length (in air) 55.30 63.33 71.16 d50.31 13.29 24.64 d11 20.93 7.05 0.54 d17 2.07 6.88 6.31 d19 5.64 11.2218.63 d21 5.71 4.25 0.38 Unit focal length f1 = 36.60 f2 = −5.70 f3 =9.61 f4 = −12.27 f5 = 16.64

Example 5

unit mm Surface data Surface No r d nd νd Object plane ∞ ∞  1 26.7830.90 1.63493 23.90  2 16.925 0.90  3 28.000 1.80 1.53110 55.91  4 84.5660.15  5 15.407 2.50 1.49700 81.54  6 338.274 Variable  7 12168.970 0.301.83481 42.71  8 5.368 2.60  9* −11.502 0.40 1.74156 49.21 10* 20.8540.10 11 12.658 1.25 1.94595 17.98 12 −178.364 Variable 13(stop) ∞ 0.6614* 6.126 1.87 1.58313 59.38 15* −25.571 1.30 16 37.078 0.40 1.9108235.25 17 4.697 2.31 1.48749 70.23 18 −12.414 Variable 19 −18.971 0.501.53110 55.91 20 17.585 Variable 21* 157.227 1.90 1.53110 55.91 22*−9.000 Variable 23 ∞ 0.30 1.51633 64.14 24 ∞ 0.40 25 ∞ 0.50 1.5163364.14 26 ∞ 0.53 Image plane ∞ (Image pickup surface) Aspherical surfacedata 9th surface K = 0.000 A4 = 7.14419e−04, A6 = −9.92786e−06, A8 =−9.58646e−08 10th surface K = 0.000 A4 = 6.15831e−04, A6 = −1.93202e−0514th surface K = 0.000 A4 = −3.75974e−04, A6 = 8.77096e−07, A8 =−5.33360e−07, A10 = −1.13725e−08 15th surface K = 0.000 A4 =3.00622e−04, A6 = 5.43055e−07, A8 = −5.32866e−07 21th surface K = 0.000A4 = −5.97082e−04 22th surface K = 0.000 A4 = −2.46536e−04, A6 =3.88957e−06, A8 = −9.51803e−08 Zoom data WE ST TE Focal length 4.4921.05 103.77 Fno. 2.89 5.00 7.02 Angle of field 2ω 90.32 20.20 4.24 fb(in air) 9.15 5.42 2.45 Lens total length (in air) 52.51 60.73 69.74 d60.31 10.56 20.81 d12 18.50 6.71 0.54 d18 2.11 12.44 15.55 d20 2.61 5.7610.55 d22 7.69 3.96 0.99 Unit focal length f1 = 33.30 f2 = −5.62 f3 =10.73 f4 = −17.10 f5 = 16.09

FIGS. 6A to 6L, 7A to 7L, 8A to 8L, 9A to 9L, and 10A to 10Lrespectively show aberrations of the zoom lenses according to the firstto fifth examples in the state in which the zoom lenses are focused onan object point at infinity. FIGS. 6A to 6L are aberration diagrams ofthe zoom lens according to the first example in the state in which thezoom lens is focused on an object point at infinity. FIGS. 6A, 6B, 6C,and 6D respectively show spherical aberration (SA), astigmatism (AS),distortion (DT), and chromatic aberration of magnification (CC) at thewide angle end. FIGS. 6E, 6F, 6G, and 6H respectively show sphericalaberration, astigmatism, distortion, and chromatic aberration ofmagnification of the zoom lens in the intermediate focal length state.FIGS. 6I, 6J, 6K, and 6L respectively show spherical aberration,astigmatism, distortion, and chromatic aberration of magnification ofthe zoom lens at the telephoto end. FIGS. 7A to 7L are aberrationdiagrams of the zoom lens according to the second example in the statein which the zoom lens is focused on an object point at infinity. FIGS.7A, 7B, 7C, and 7D respectively show spherical aberration, astigmatism,distortion, and chromatic aberration of magnification of the zoom lensat the wide angle end. FIGS. 7E, 7F, 7G, and 7H respectively showspherical aberration, astigmatism, distortion, and chromatic aberrationof magnification of the zoom lens in the intermediate focal lengthstate. FIGS. 7I, 7J, 7K, and 7L respectively show spherical aberration,astigmatism, distortion, and chromatic aberration of magnification ofthe zoom lens at the telephoto end. FIGS. 8A to 8L are aberrationdiagrams of the zoom lens according to the third example in the state inwhich the zoom lens is focused on an object point at infinity. FIGS. 8A,8B, 8C, and 8D respectively show spherical aberration, astigmatism,distortion, and chromatic aberration of magnification of the zoom lensat the wide angle end. FIGS. 8E, 8F, 8G, and 8H respectively showspherical aberration, astigmatism, distortion, and chromatic aberrationof magnification of the zoom lens in the intermediate focal lengthstate. FIGS. 8I, 8J, 8K, and 8L respectively show spherical aberration,astigmatism, distortion, and chromatic aberration of magnification ofthe zoom lens at the telephoto end. FIGS. 9A to 9L are aberrationdiagrams of the zoom lens according to the fourth example in the statein which the zoom lens is focused on an object point at infinity. FIGS.9A, 9B, 9C, and 9D respectively show spherical aberration, astigmatism,distortion, and chromatic aberration of magnification of the zoom lensat the wide angle end. FIGS. 9E, 9F, 9G, and 9H respectively showspherical aberration, astigmatism, distortion, and chromatic aberrationof magnification of the zoom lens in the intermediate focal lengthstate. FIGS. 9I, 9J, 9K, and 9L respectively show spherical aberration,astigmatism, distortion, and chromatic aberration of magnification ofthe zoom lens at the telephoto end. FIGS. 10A to 10L are aberrationdiagrams of the zoom lens according to the fifth example in the state inwhich the zoom lens is focused on an object point at infinity. FIGS.10A, 10B, 10C, and 10D respectively show spherical aberration,astigmatism, distortion, and chromatic aberration of magnification ofthe zoom lens at the wide angle end. FIGS. 10E, 10F, 10G, and 10Hrespectively show spherical aberration, astigmatism, distortion, andchromatic aberration of magnification of the zoom lens in theintermediate focal length state. FIGS. 10I, 10J, 10K, and 10Lrespectively show spherical aberration, astigmatism, distortion, andchromatic aberration of magnification of the zoom lens at the telephotoend. In aberration diagrams, co represents the half angle of view.

Next, parameter and values of conditional expressions in eachembodiments are described.

Conditional expressions Example 1 Example 2 Example 3 Example 4 Example5 (1) 3.304 3.061 3.026 3.708 3.218 (2) 0.295 0.303 0.34 0.271 0.364 (3)0.248 0.296 0.239 0.302 0.274 (4) 0.178 0.148 0.192 0.12 0.166 (5),(5-1), 28.818 23.042 23.067 28.615 23.107 (5-2) (6) −0.044 −0.056 −0.05−0.043 −0.054 (7) 0.066 0.055 0.07 0.067 0.069 D_(G1G223) at WE (8)0.066 — — 0.067 — D_(G1G228) at WE

Example 1 Example 2 Example 3 Example 4 Example 5 f_(t) 131.117 104.859101.699 132.200 103.767 D_(G1ASt) 39.679 34.259 33.612 35.651 32.251D_(ASIMt) 38.743 31.741 34.557 35.772 37.758 D_(G2G3w) 19.430 19.54016.260 21.590 19.160 D_(G1IMt) 78.422 66.000 68.169 71.423 70.009D_(G1IMw) 55.046 50.464 48.680 55.571 52.776 f_(w) 4.550 4.551 4.4094.620 4.491 f_(G2) −5.792 −5.904 −5.074 −5.697 −5.619 D_(G1G223) at0.300 0.250 0.310 0.310 0.310 WE D_(G1G228) at 0.300 — — 0.310 — WE(Digital Camera)

The image pickup apparatus according to the present invention that formsan image of an object by a zoom lens and picks up the image by receivingit by an electronic image pickup element such as a CCD can be applied toan electronic image pickup apparatus, in particular to a digital cameraor a video camera. In the following, an embodiment of the electronicimage pickup apparatus will be described.

FIG. 11A and FIG. 11B are cross-sectional views of a digital camera inwhich, the zoom lens according to the present invention is installed,where, FIG. 11A is a cross-sectional view when collapsed to accommodate,and FIG. 11B is a cross-sectional view at the wide angle end.

At the time of collapsing to accommodate the zoom lens, the first lensunit G1 moves along a direction D1, the second lens unit G2 moves alonga direction D2, the fourth lens unit G4 moves along a direction D4, andthe fifth lens unit G5 moves along a direction D5, thus each of the lensunits G1, G2, G4, and G5 moving toward the image pickup element (towardthe image plane I) along the respective optical axis. The third lensunit G3 and the aperture stop S are withdrawn from an optical axis AX ofthe other lens units, and are collapsed into a body 51 upon undergoingdecentered movement along a direction D3. Accordingly, the zoom lensbecomes a zoom lens with a high zoom ratio in which, small-sizing ofradius of the first lens unit G1 is made possible.

A lens barrier section 60 in which, a lens barrel 52 is built-in isdisposed at a front side (object side) of the first lens unit G1.

The lens barrier section 60 includes a fixed portion 61 which is fixedto the lens barrel 52, and movable portions 62 and 63 which are movablein a planar direction orthogonal to the optical axis AX, as a pluralityof barrier members. The movable portions 62 and 63, when the zoom lensis not in use, move toward an inner side of the fixed portion 61shutting the optical path, and when the zoom lens is in use, areretracted away from an effective optical path.

As an example of a concrete arrangement of the lens barrier section 60,a barrier described in Japanese Patent Application Laid-open PublicationNo. 2012-203135 by the applicant of the present patent application, canbe used.

In the zoom lens according to the present invention, an electricaldistortion correction is carried out for each of RGB (red, green, andblue), and the distortion and the chromatic aberration of magnificationare corrected electrically.

FIG. 12 and FIG. 13 are conceptual diagrams of an arrangement of animage pickup apparatus according to the present invention in which, thezoom lens is installed in an image pickup optical system 41. FIG. 12 isa front perspective view showing an appearance of a digital camera 40 asthe image pickup apparatus, and FIG. 13 is a rear perspective viewshowing an appearance of the digital camera 40.

The digital camera 40 of this embodiment includes the image pickupoptical system 41 positioned on an optical path for photography 42, ashutter button 45, and a liquid-crystal display monitor 47. As theshutter button 45 disposed on an upper portion of the digital camera 40is pressed, in conjunction with the pressing of the shutter button 45,photography is carried out by the image pickup optical system 41, bycapturing through the zoom lens of the example 1 for instance. An objectimage formed by the image pickup optical system 41 is formed on an imagepickup element (opto-electric conversion surface) which is provided nearan image forming surface. The object image received by the image pickupelement is displayed on the liquid-crystal display monitor 47 providedon a rear surface of the digital camera, as an electronic image by aprocessing unit. Moreover, it is possible to record the electronic imagecaptured, in a recording unit.

(Internal Circuit Structure)

FIG. 14 is a block diagram showing an internal circuit of maincomponents of the digital camera 40. In the following description, theprocessing unit mentioned above includes components such as CDS/ADCsection 24, a temporary storage memory section 17, and an imageprocessing section 18. A storage unit includes a storage medium

As shown in FIG. 14, the digital camera 40 includes an operating section12, a control section 13 which is connected to the operating section 12,an imaging drive circuit 16 which is connected to a control-signaloutput port of the control section 13 via buses 14 and 15, the temporarystorage memory section 17, the image processing section 18, a storagemedium section 19, a display section 20, and a set-information storagememory section 21.

The temporary storage memory section 17, the image processing section18, the storage medium section 19, the display section 20, and theset-information storage memory section 21 are capable of inputting andoutputting data mutually via a bus 22. Moreover, a CCD 49 and theCDS/ADC section 24 are connected to the imaging drive circuit 16.

The operating section 12 includes various input buttons and switches,and imparts event information input from outside (user of camera) viathe input buttons and switches to the control section 13. The controlsection 13 is a central arithmetic processing unit such as a CPU with abuilt-in program memory which is not shown in the diagram, and controlsthe overall digital camera according to a computer program which hasbeen stored in the computer program memory.

The CCD 49 is an image pickup element which is driven and controlled bythe imaging drive circuit 16, and which converts an amount of light foreach pixel of the object image which has been formed through the imagepickup optical system 41 to an electric signal, and outputs to theCDS/ADC section 24.

The CDS/ADC section 24 is a circuit which amplifies the electric signalinput from the CCD 49, and also carries out analog-to-digitalconversion, and outputs image raw-data only for the amplification anddigital conversion carried out (bayer data, hereinafter called as ‘RAWdata’).

The temporary storage memory section 17 is a buffer such as a SDRAM, andis a memory unit which temporarily stores the RAW data output put fromthe CDS/ADC section 24. The image processing section 18 is a circuitwhich reads the RAW data which has been stored in the temporary storagememory section 17 or the RAW data which has been stored in the storagemedium section 19, and carries out electrically, various imageprocessing including a distortion correction based on image-qualityparameters which have been specified by the control section 13.

The recording medium section 19 in which, a recording medium in the formof a stick or a card with a flash memory is detachably mounted, recordsand maintains the RAW data which is transferred from the temporarystorage memory section 17 and image data which has been subjected toimage processing in the image processing section 18.

The display section 20 includes the liquid-crystal display monitor 47and displays operation menu, image data, and RAW data captured. Theset-information storage memory section 21 is provided with a ROM sectionin which various image-quality parameters are stored in advance, and aRAM section which stores the image-quality parameters which have beenread from the ROM section by an input and output operation of theoperating section 12.

As it has been described above, the zoom lens and the image pickupapparatus using the same according to the present invention are usefulfor securing a high zoom ratio of a zoom lens, for securing an opticalperformance, and for small-sizing of a zoom lens.

The zoom lens and the image pickup apparatus using the same according tothe present invention show an effect that the zoom lens and the imagepickup apparatus are useful for securing a high zoom ratio of a zoomlens, for securing an optical performance, and for small-sizing of azoom lens.

What is claimed is:
 1. A zoom lens comprising in order from an objectside to an image side: a first lens unit having a positive refractivepower; a second lens unit having a negative refractive power; a thirdlens unit having a positive refractive power; and a fourth lens unithaving a negative refractive power, wherein the zoom lens furtherincludes an aperture stop which is disposed between the second lens unitand the fourth lens unit, and the first lens unit includes a negativelens and a plurality of positive lenses, and at the time of zooming froma wide angle end to a telephoto end, a distance between the first lensunit and the second lens unit widens, a distance between the second lensunit and the third lens unit narrows, and a distance between the thirdlens unit and the fourth lens unit changes, and the followingconditional expressions (1) and (2) are satisfied2.85 <f _(t) /D _(G1ASt)<7.40  (1)0.2 <D _(ASIMt) /f _(t)<0.40  (2) where, f_(t) denotes a focal length ofthe overall zoom lens system at the telephoto end, D_(G1ASt) denotes adistance on an optical axis from an object-side surface of a lensnearest to the object side in the first lens unit up to the aperturestop, at the telephoto end, and D_(ASIMt) denotes a distance on theoptical axis from the aperture stop up to an image, at the telephotoend.
 2. The zoom lens according to claim 1, wherein the followingconditional expression (3) is satisfied0.16<D _(G2G3w) /D _(G1IMt)<0.6  (3) where, D_(G2G3w) denotes a distanceon the optical axis between the second lens unit and the third lens unitat the wide angle end, and D_(G1IMt) denotes a distance on the opticalaxis from the object-side surface of the lens nearest to the object sidein the first lens unit up to the image, at the telephoto end.
 3. Thezoom lens according to claim 2, wherein the following conditionalexpressions (5-2) and (8) are satisfied28<f _(t) /f _(w)<50  (5-2)0.010<D _(G1G228) /f _(w)<0.07  (8) where, D_(G1G228) denotes a distancebetween the first lens unit and the second lens unit, in an arbitrarystate in which, the focal length is shorter than f_(t)/28.
 4. The zoomlens according to claim 1, wherein the following conditional expression(4) is satisfied0.0521 (D _(G1IMt) −D _(G1IMw))/f _(t)<0.22  (4) where, D_(G1IMt)denotes a distance on the optical axis from an object-side surface ofthe lens nearest to the object side in the first lens unit up to theimage, at the telephoto end, D_(G1IMw) denotes a distance on the opticalaxis from the object-side surface of the lens nearest to the object sidein the first lens unit up to the image, at the wide angle end.
 5. Thezoom lens according to claim 1, further comprising: an image-side lensunit having a positive refractive power, which is disposed on an imageside of the fourth lens unit, wherein at the time of zooming from thewide angle end to the telephoto end a distance between the fourth lensunit and the image-side lens unit changes, and the first lens unit ispositioned on the object side at the telephoto end, than a position atthe wide angle end, and the image-side lens unit is positioned on theimage side at the telephoto end, than a position at the wide angle end.6. The zoom lens according to claim 1, wherein the following conditionalexpression (5) is satisfied20<f _(t) /f _(w)<50  (5) where, f_(w) denotes a focal length of theoverall zoom lens system at the wide angle end.
 7. The zoom lensaccording to claim 1, wherein the second lens unit satisfies thefollowing conditional expression (6)−0.06<f _(G2) /f _(t)<−0.03  (6) where, f_(G2) denotes a focal length ofthe second lens unit.
 8. The zoom lens according to claim 1, wherein thefirst lens unit is positioned on the object side at the telephoto end,than a position at the wide angle end, the second lens unit ispositioned on the image side at the telephoto end, than a position atthe wide angle end, the third lens unit is positioned on the object sideat the telephoto end, than a position at the wide angle end, and thefourth lens unit is positioned on the object side at the telephoto end,than a position at the wide angle end.
 9. The zoom lens according toclaim 1, wherein the aperture stop is disposed immediately before theobject side of the third lens unit, and the third lens unit and theaperture stop move integrally along the optical axis, and are positionedon the object side at the telephoto end than a position at the wideangle end.
 10. The zoom lens according to claim 1, wherein the secondlens unit includes maximum of three lenses.
 11. The zoom lens accordingto claim 1, wherein the third lens unit includes maximum of four lenses.12. The zoom lens according to claim 1, wherein the fourth lens unitincludes only one lens component, and the lens component is a lens ofwhich, only two surfaces namely, an object-side surface and animage-side surface make a contact with air, in an optical path.
 13. Thezoom lens according to claim 1, wherein the zoom lens includes animage-side lens unit having a positive refractive power, which isdisposed on the image side of the fourth lens unit, and at the time ofzooming from the wide angle end to the telephoto end, a distance betweenthe fourth lens unit and the image-side lens unit changes, and the zoomlens is a five-unit zoom lens.
 14. An image pickup apparatus comprising:a zoom lens; and an image pickup element which is disposed on an imageside of the zoom lens, and which converts an image formed by the zoomlens to an electric image, wherein the zoom lens is the zoom lensaccording to claim
 1. 15. The image pickup apparatus according to claim14, wherein the image pickup apparatus has on an object side of thefirst lens unit, a lens barrier section having a plurality of barriermembers which retract in a direction perpendicular to an optical axis.16. A zoom lens comprising in order from an object side to an imageside: a first lens unit having a positive refractive power; a secondlens unit having a negative refractive power; a third lens unit having apositive refractive power; and a fourth lens unit having a negativerefractive power, wherein the zoom lens further includes an aperturestop which is disposed between the second lens unit and the fourth lensunit, and the first lens unit includes a negative lens and a pluralityof positive lenses, and at the time of zooming from a wide angle end toa telephoto end, a distance between the first lens unit and the secondlens unit widens, a distance between the second lens unit and the thirdlens unit narrows, and a distance between the third lens unit and thefourth lens unit changes, and the following conditional expressions (1)and (3) are satisfied2.85<f _(t) /D _(G1ASt)<7.40  (1)0.16<D _(G2G3w) /D _(G1IMt)<0.6  (3) where, f_(t) denotes a focal lengthof the overall zoom lens system at the telephoto end, D_(G1ASt) denotesa distance on an optical axis from an object-side surface of a lensnearest to the object side in the first lens unit up to the aperturestop, at the telephoto end, D_(G2G3w) denotes a distance on the opticalaxis between the second lens unit and the third lens unit at the wideangle end, and D_(G1IMt) denotes a distance on the optical axis from theobject-side surface of the lens nearest to the object side in the firstlens unit up to an image, at the telephoto end.
 17. A zoom lenscomprising in order from an object side to an image side: a first lensunit having a positive refractive power; a second lens unit having anegative refractive power; a third lens unit having a positiverefractive power; and a fourth lens unit having a negative refractivepower; wherein the zoom lens further includes an aperture stop which isdisposed between the second lens unit and the fourth lens unit, and thefirst lens unit includes a negative lens and a plurality of positivelenses, and at the time of zooming from a wide angle end to a telephotoend, a distance between the first lens unit and the second lens unitwidens, a distance between the second lens unit and the third lens unitnarrows, and a distance between the third lens unit and the fourth lensunit changes, and the following conditional expressions (1) and (4) aresatisfied2.85<f _(t) /D _(GIAst)<7.40  (1)0.05<(D _(G1IMt) −D _(G1IMw))/f _(t)<0.22  (4) where, f_(t) denotes afocal length of the overall zoom lens system at the telephoto end,D_(G1ASt) denotes a distance on an optical axis from an object-sidesurface of a lens nearest to the object side in the first lens unit upto the aperture stop, at the telephoto end, D_(G1IMt) denotes a distanceon the optical axis from an object-side surface of the lens nearest tothe object side in the first lens unit up to an image, at the telephotoend, D_(G1IMw) denotes a distance on the optical axis (optical axialdistance) from the object-side surface of the lens nearest to the objectside in the first lens unit up to the image, at the wide angle end. 18.A zoom lens comprising in order from an object side to an image side: afirst lens unit having a positive refractive power; a second lens unithaving a negative refractive power; a third lens unit having a positiverefractive power; and a fourth lens unit having a negative refractivepower, wherein the zoom lens further includes an image-side lens unithaving a positive refractive power, which is disposed on the image sideof the fourth lens unit, and an aperture stop which is disposed betweenthe second lens unit and the fourth lens unit, and the first lens unitincludes a negative lens and a plurality of positive lenses, and at thetime of zooming from a wide angle end to a telephoto end, a distancebetween the first lens unit and the second lens unit widens, a distancebetween the second lens unit and the third lens unit narrows, a distancebetween the third lens unit and the fourth lens unit changes, and adistance between the fourth lens unit and the image-side lens unitchanges, and the first lens unit is positioned on the object side at thetelephoto end, than a position at the wide angle end, and the image-sidelens unit is positioned on the image side at the telephoto end, than aposition at the wide angle end, and the following conditional expression(1) is satisfied2.85<f _(t) /D _(G1ASt)<7.40  (1) where, f_(t) denotes a focal length ofthe overall zoom lens system at the telephoto end, and D_(G1ASt) denotesa distance on an optical axis from an object-side surface of a lensnearest to the object side in the first lens unit up to the aperturestop, at the telephoto end.
 19. The zoom lens according to claim 18,wherein the image-side lens unit includes one lens component, and thelens component is a lens of which, only two surfaces namely, anobject-side surface and an image-side surface make a contact with air,in an optical path.
 20. A zoom lens comprising in order from an objectside to an image side: a first lens unit having a positive refractivepower; a second lens unit having a negative refractive power; a thirdlens unit having a positive refractive power; and a fourth lens unithaving a negative refractive power, wherein the zoom lens furtherincludes an aperture stop which is disposed between the second lens unitand the fourth lens unit, and the first lens unit includes a negativelens and a plurality of positive lenses, and at the time of zooming froma wide angle end to a telephoto end, a distance between the first lensunit and the second lens unit widens, a distance between the second lensunit and the third lens unit narrows, and a distance between the thirdlens unit and the fourth lens unit changes, and the followingconditional expressions (1) and (5) are satisfied2.85<f _(t) /D _(G1ASt)<7.40  (1)20<f _(t) /f _(w)<50  (5) where, f_(t) denotes a focal length of theoverall zoom lens system at the telephoto end, D_(G1ASt) denotes adistance on an optical axis from an object-side surface of a lensnearest to the object side in the first lens unit up to the aperturestop, at the telephoto end, and f_(w) denotes a focal length of theoverall zoom lens system at the wide angle end.
 21. The zoom lensaccording to claim 20, wherein the following conditional expressions(5-1) and (7) are satisfied23<f _(t) /f _(w)<50  (5-1)0.010<D _(G1G223) /f _(w)<0.07  (7) where, D_(G1G223) denotes a distancebetween the first lens unit and the second lens unit, in an arbitrarystate in which, the focal length becomes shorter than f_(t)/23.